Introduction to Functional Groups

As we have seen, the number of possible organic compounds is virtually limitless. How can anyone learn the chemistry of all of them Fortunately, we do not need to learn an entire new set of chemical reactions for each new compound encountered. A particular arrangement or group of atoms has very similar chemistry no matter what the remainder of the molecule looks like. 

RH ch3ch2ch3 Alkane (Alkanes have no functional group.) 

RCH=CH, CH3CH2CH=CH2 Alkene (The functional group is the carbon—carbon double bond.) 

ArH Arene (A six-membered ring with three double bonds has different reactions than an alkene so it is given a different name. Arenes or aromatic rings can have alkyl or 

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The Lead-Off Reaction Addition of HBr to Alkenes Students usually attach great-importance to a text s lead-off reaction because it is the first reaction they see and is discussed in such detail. 1 use the addition of HBr to an alkene as the lead-off to illustrate general principles of organic chemistry for several reasons the reaction is relatively straightforward it involves a common but important functional group no prior knowledge of stereochemistry or kinetics in needed to understand it and, most important, it is a polar reaction. As such, 1 believe that electrophilic addition reactions represent a much more useful and realistic introduction to functional-group chemistry than a lead-off such as radical alkane chlorination. 

Physical Properties and Molecular Structure 2.7 Introduction to Functional Groups Mastery Goal Quiz Molecular Model Problems... 

INTRODUCTION TO FUNCTIONAL GROUPS HYDROCARBONS AND HALOALKANES Hydrocarbons... 

Polymer Modification. The introduction of functional groups on polysdanes using the alkah metal coupling of dichlorosilanes is extremely difficult to achieve. Some polymers and copolymers with 2-(3-cyclohexenyl)ethyl substituents on siUcon have been made, and these undergo hydrogen hahde addition to the carbon—carbon double bond (94,98). 

The pharmaceutical interest in the tricyclic structure of dibenz[6,/]oxepins with various side chains in position 10(11) stimulated a search for a convenient method for the introduction of functional groups into this position. It has been shown that nucleophilic attack at the carbonyl group in the 10-position of the dibenzoxepin structure renders the system susceptible to water elimination. Formally, the hydroxy group in the enol form is replaced by nucleophiles such as amines or thiols. The Lewis acids boron trifluoride-diethyl ether complex and titanium(IV) chloride have been used as catalysts. 

Some transition metal catalysts induce the living polymerization of various acetylenic compounds.68,69 Such polymerizations of phenylacetylene catalyzed by rhodium complexes are used in conjunction with a quantitative initiation and introduction of functional groups at the initiating chain end (Scheme 16).70 The catalyst is prepared from an [RhCl(nbd)]2/Ph2C=C(Ph)Li/PPh3 mixture and proceeds smoothly to give quantitatively the polymer 54 with a low polydispersity ratio. 

C-C bond formation using the Heck reaction allows the introduction of functional groups to obtain new organic structures on solid supports. This reaction between an alkene with an alkenyl or an aryl halide has been widely employed in various in-tra- and inter-molecular versions on solid-phase because of the readily accessibility of starting materials. The Heck reaction was performed on immobilized aryl or alkenyl halides with soluble alkenes and vice versa (Scheme 3.11). 

To make these substrates suitable for biological assays, the introduction of functional groups that can be traced with the proper analytical techniques is essential. The use of radio-, fluorescent-, and biotin-labeled lipidated peptides has been reported. The synthesis of fluorescent substrates is chemically straightforward and allows for production of larger quantities than the enzymatic synthesis used for radiolabeled peptides and is thus preferred over the use of radioactive compounds. [1 21] Common fluorescent probes can be introduced by conjugation to a free functional group present in the peptide. The fluorescent moiety is... 

The introduction of functional groups is suitable to control the chemical and physical properties of the polymer. However, the introduction of functional groups may cause a reaction of the unshared electron pairs of the functional groups with the active catalytic sites. Thus, the active sites of the catalyst are destroyed. In order to overcome this problem, a procedure has been developed, where the functionalized monomers, such as maleic acid, nadic acid or their anhydrides are grafted after the polymerization reaction (4,37). Grafting takes place as a radical reaction, using e.g., dicumyl peroxide. Other attempts use excessive amounts of catalysts. 

The methyl group in 5-methylindolizines is sufficiently active to allow the introduction of functional groups. Indolizines (15) with n-butyllithium followed by A,A-dimethylamides give, after hydrolysis, ketones 16. Cyclodehydration to 1 takes place in glacial acetic acid [Eq. (1)] more severe conditions, such as in hydrogen fluoride, were ineffective, presumably owing to protonation of the indolizine nucleus.1... 

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